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What if there were a potentially-life saving material that the US medical community were perpetually short of? Unfortunately, that's the reality of the nation's blood supply. A combination of disinterest and rigorous screening have left the country in a perpetual state of blood shortage. In a development that may point the way towards making time spent bleeding through a needle in your arm a thing of the past, researchers in Japan have developed a technique that induces human embryonic stem cells to form mature, blood carrying erythrocytes.

Most people are probably aware that stem cells in the bone marrow are responsible for replenishing the supply of red blood cells that carry oxygen throughout the body. Less well known is the fact that the bone marrow is actually the third stop for these stem cells. In mammalian embryonic development, these cells arise initially in tissue that's outside the body and destined to be lost at birth. From there, they initially take up residence in the fetal liver. It's only late in development that they migrate to the bone marrow.

The researchers behind the new research reasoned that the fetal liver was more than a passive residence, and instead was likely to produce factors that promoted the production of blood cells. So, they isolated fetal liver cells from mice and cultured human embryonic stem cells with them. After ten days of culture, the first indications of red cell formation were visible, as hemoglobin expression started. By twenty days, many cells were producing adult forms of hemoglobin, and many cells had eliminated their nucleus, a typical sign of red cell maturity.

Tests with the resulting cells indicate that they have oxygen carrying capacity and express enzymes that are used for coping with oxygen-related stress. The oxygen dissociation curves show that these cells behave a bit like fetal red blood cells (as might be expected), as they have a higher affinity for oxygen.

Still, that sort of behavior could be more than sufficient for emergency applications, especially given that some of the alternative approaches for dealing with the blood shortage aren't very good. Still, there's a long way between these results and practical applications—nobody's going to want to dissect out enough fetal mouse livers to get this to work on an industrial scale.

Still, as the authors themselves note, a functioning system like this is a key first step towards studying what's needed to eliminate its reliance on animal cells and scale it up for practical use. So, it will definitely be a minimum of several years before we're likely to have a stem cell based blood supply.